1. Field
Embodiments of the present invention relate to an energy storage system that can be charged using energy from the external device and a driving method thereof.
2. Description of the Related Art
Recently, batteries have been widely used in not only mobile electronic devices, such as smart phones and tablet PCs, but also vehicles such as cars. Particularly, when a battery is used in a vehicle, a high voltage is used in the vehicle, and hence the battery may be used in the form of a battery pack in which a plurality of batteries are coupled in series to each other. Also, a high charge or energy capacity is useful in the vehicle, and hence the battery may be used in a form in which battery packs are coupled in parallel to each other.
The plurality of battery packs coupled in parallel to each other may be charged or discharged while moving together with the vehicle. Although the battery packs coupled in parallel are concurrently charged or discharged, the states of charge (SOCs) of the battery packs may be different from one another. When the battery packs having different charge states are charged at the same time, one of the batteries may be overcharged. When a lithium-ion battery (Li-ion battery) is overcharged, there may be a risk that the battery will catch fire or explode. The SOC has a value from 0% to 100%. Here, 100% represents a state in which the battery is fully charged, and 0% represents a state in which the battery is completely discharged.
The overdischarge of each battery pack may be prevented or substantially prevented by measuring a SOC of each battery pack, and by controlling current such that the SOC of each battery pack is not changed. However, the number of components used for current control increases, and therefore, price increases.